The driver, reinstated by NASCAR last month after failing a random drug test in July, will replace Regan Smith in the No. 51 car for the Bank of America 500; Smith replaces Dale Earnhardt Jr., who is out with concussion symptoms.

AJ Allmendinger is taking advantage of NASCAR's twists and turns to get another chance on a Sprint Cup oval.

Allmendinger, reinstated by NASCAR last month after failing a random drug test in July, will get a chance to resurrect his career with appropriately named Phoenix Racing on Sunday, replacing Regan Smith as the driver of the No. 51 car.

Allmendinger's chance comes because Smith—whose name still appeared above the No. 51 garage stall at Charlotte Motor Speedway on Thursday—will replace Dale Earnhardt Jr. in the No. 88 car for the Bank of America 500.

Earnhardt will sit out at least the next two races, suffering from concussion symptoms, which recurred after a 25-car pileup on the last lap at Talladega on Sunday.

In the meantime, Earnhardt's medical situation provides Smith a chance to step into the Chase-quality ride at Hendrick Motorsports.

Smith, 29, had his best finish of the season on Sunday, maneuvering through the final-lap mayhem to end up fifth.

Rick Hendrick, owner of Earnhardt's car, said he called Phoenix Racing team owner James Finch about 10 p.m. Wednesday, requesting permission to use Smith as his driver on Sunday. It was a logical move for Hendrick Motorsports, which has designs on employing Smith next season.

Phoenix Racing has a technical alliance with Hendrick Motorsports.

Allmendinger, 30, has had success at Charlotte this season. He finished second from the pole in the Sprint Showdown, earning a spot in the All-Star Race this spring.

Many in the garage openly questioned when and if Allmendinger would get another chance in a Cup car after being released by Penske Racing in the wake of testing positive for Adderall, a prescription drug often associated with the treatment of attention deficit disorder.

Allmendinger also was arrested for DUI by Mooresville, North Carolina, police in October 2009, resulting in probation by NASCAR for the remainder of that season.

Harrison said Finch had previously considered putting Allmendinger in the No. 51 car before offering the ride to Smith.

Allmendinger had a pair of top-10 Cup finishes last year at Charlotte, finishing fifth and seventh while driving for Richard Petty Motorsports.